1. Field of Invention
This invention relates to a vehicle body painting system having a paint recovery sub-system for minimizing the paint requirements.
2. Description of Prior Developments
In conventional automotive vehicle manufacture the vehicle bodies are painted in a tunnel-type paint booth. Typically, the bodies are placed on a conveyor that moves slowly through different chambers in an elongated tunnel. As each vehicle moves slowly along the tunnel, different painting operations and drying operations are performed on different surfaces of the vehicle.
Different paint colors are applied to the different vehicle bodies, depending on production requirements. Periodically, it is necessary to change the paint coloration supplied to the paint applicator mechanisms, e.g. when one vehicle is to have a blue coloration and the next vehicle body is to have a red coloration.
When it is necessary to change the paint coloration supplied to the paint applicator mechanisms, a paint solvent is passed through the paint supply passages, paint applicator mechanisms, and paint return passages. The solvent initially acts as a pump to move most of the paint out of the passages, and later as a cleaner to dissolve and remove residual paint from the passage walls. The process of removing paint from the various passages is sometimes referred to as the purge cycle. Typically the purge cycle takes about fifteen seconds. The purge cycle takes place without stopping the conveyor. The vehicle bodies continually move through the paint booth tunnel during the purge cycle and during the time required to load the new paint coloration into the various passages.
Under conventional practice, paint purged from the painting mechanism is sent to a common paint collection receptacle. Over time paint colorations of various hues and shades are comingled so as to be unusable. A typical painting system may have about ten different paint colorations. Mixing ten different colors produces a substantially unusable paint coloration.
U.S. Pat. No. 3,348,774, issued to R. Wiggins, discloses a painting system, wherein the paint coloration change cycle includes a purge action that reclaims some of the purged paint in a relatively pure condition. The patent shows a pure paint reclaim container and a separate common paint disposal container having a branched connection to a purge line so that during the initial stage of the purge cycle paint is directed to the reclaim container and during the later stage paint is sent to the common disposal container. The patent does not disclose how the paint path is switched or redirected.